Significant flooding has occurred in southwest Connecticut

A nearly stationary band of very heavy rainfall set up across southwest Connecticut Sunday afternoon, leading to extreme rainfall. Estimated totals are currently showing 4-8+ inches of rain having fallen across a narrow section of Connecticut. This came as a frontal system has been very slowly moving eastward over the past couple days due to offshore high pressure and the distant Hurricane Ernesto.

Estimated 6 hour rainfall totals from Sunday afternoon as of Sunday afternoon:

Photo byNational Weather Service

The communities of Southbury and Danbury were hit particularly hard. Fairfield and New Haven counties were put under a flash floods emergency for Sunday afternoon. This rare alert is issued only for flooding events that have turned truly dire and very dangerous. Several roads in Southbury have been washed out and closed, including all lanes of Route 172. Multiple scenes of vehicles underwater in roadways from the community have emerged.

In Danbury, a mudslide has been reported to have caused a major gas leak early in the afternoon. A building was evacuated, but the gas leak situation has been reported to be "isolated and under control." Other buildings in Danbury were evacuated due to flooding. Woodbury, Connecticut has also reported numerous roads around the town as underwater and impassible.

Flooding in SouthburyPhoto byBobby Ellison

In Monroe, Connecticut, multiple motorists have been reported to be stranded in flood waters. Water rescues are ongoing as of late Sunday afternoon in the area by the fire department. Earlier in the day, water rescues occurred across Sanford, Connecticut, mainly in the late morning. Substantial river flooding has been reported in nearby New Canaan.

Flooding in the Southbury areaPhoto byMatt Austin

The main flood threat for Sunday was expected to be farther west. A flood watch was posted for portions of New Jersey, New York and Pennsylvania. Far western Connecticut was included in the "slight" (level 2 of 4) chance for excessive rainfall this morning. So far, the area where the initial flood watch was issued has seen minimal issues with flooding (though severe thunderstorms are moving through the area). Late Sunday afternoon, the flood watch was expanded to include southwest Connecticut.

The green area is where flood watches were issued this morning. Red areas indicate flash flood warnings as of 4pm:

Photo byNational Weather Service

High resolution guidance generally depicted 1-2 inches of rainfall occurring to the west of New England today, which prompted the above flood watch. The slow-moving nature of the system interacting with a moisture-rich atmosphere led to these very high rain totals. The high resolution error zone was about 50-60 miles, meaning the heaviest rainfall today fell about 50-60 miles farther east than anticipated.

This event is starkly reminiscent of the surprise major flooding event that took place in the Northeast Kingdom of Vermont on July 30th. That night, a cutoff low pressure system dropped 4-8 inches of rain in a narrow area of northeast Vermont after rapidly strengthening. Today, a very slow moving frontal system led to a stationary band of thunderstorms setting up over southwest Connecticut.

NAM rainfall prediction from yesterday evening:

Photo byNAM/WeatherBELL

Heading into Sunday evening, the band of storms that brought southwest Connecticut significant flooding is slowly pushing north and east. As of 5pm Sunday, thunderstorms were still moving through southwest Connecticut, but should gradually wind down this evening. More rain will come through Monday as a potent cold front crosses New England.